1. Field of the Invention
This invention relates to a method for removing toner from a sheet of paper by heating and contacting the paper containing toner with an adhesive surface so that the paper can be reused.
2. Description of the Prior Art
Two principal uses of office paper in the U.S. are in photocopiers and in printers which use a laser printing technology. Both of these processes use a toner material to create the image. The various types of toners are thermosetting plastic resins with carbon black and other minor constituents to control flow, electrical and magnetic properties. This toner is "set" onto the paper by using heat to melt the resin forming a solid film adhering to the paper surface.
Approximately 10 million tons of office paper are used annually in the U.S., and the percentage of this paper used in laser-print technology (this term includes photocopy technology) can be as high as 70%.
In addition, approximately 25,000 tons of toner is used annually in the U.S., with a total world use of 50,000 tons annually. Much of the laser printed paper is used for short term purposes and then discarded, creating a large and rapidly growing stream of office wastepaper. It is estimated that this stream of office waste will reach 12 million tons per year in the U.S. Similar trends are occurring in developed countries around the world.
This stream of laser-print wastepaper contains very high quality, bleached cellulose fibers derived from chemically pulping wood chips. To produce such high quality papers it typically requires four tons of green wood to produce one ton of paper. Unfortunately, the toner has been found to be very tenacious in its adhesion to the fiber in conventional recycling and deinking processes, and even when detached during conventional recycling the ink particles are large and difficult to separate from the pulp slurry. These deinking processes function in the wet state after the paper has been broken down into individual fibers by mechanical action in large repulper devices. This type of process is only performed at large manufacturing sites, and is not suitable for office environments.
There are also methods of ink removal which do not function in the wet state and do not require that the paper be broken down into individual fibers by mechanical action in large repulper devices, such as the use of solvents or solvent recovery employed in the patent to Mitsubishi Electronic Corp.(JP04327299).